Contents.- v.1 Three membered heterocyclic ring, v.2 Four membered hetrocycles, and all fused system with a four membered hetrocyclic ring, v.3 Five membered rings with one heteroatom, and their benzo and other carbocyclic fused derivatives, v.4 Five membered rings with two heteroatoms, and fused carbocyclic derivatives, v.5 Five membered rings: Triazoles, oxadiazoles, thiadiazoles and their fused carbocyclic derivatives, v.6 Other five membered rings with three or more heteroatoms and their fused carbocyclic derivatives, v.7 Six membered rings with one heteroatom and their fused carbocyclic derivatives, v.8 Six membered rings with two heteroatom and their fused carbocyclic derivatives, v.9 Six membered rings with three or more heteroatom and their fused carbocyclic derivatives, v.10 Ring system with at least two fused hetrerocyclic five or six membered rings with no bridgehead (ring junction) heteroatom, v.11 Bicyclic 5-5 and 5-6 fused ring systems with at least one bridgehead (ring junction) N, v.12 Five and six membered fused systems with bridgehead (ring junction)heteroatoms concluded:6-6 bicyclic with one or two N and other heteroatoms; polycyclic; spirocyclic, v.13 Seven membered hetrocyclic rings and their fused derivatives, v.14 Eight membered and large heterocyclic rings and their fused derivatives other seven membered rings, v.15 Cumulative subject index.